Terrestrial Trunk Radio (TETRA) is a global standard for radio communications on private/professional mobile radios. Professional mobile radios include radios, other than mobile telephones, such as mobile radios, portable radios, and the like. TETRA supports a trunked mode operation (TMO) and a direct mode operation (DMO). In the trunked mode, radios use network infrastructure, such as base stations, to communicate with each other. In direct mode, on the other hand, radios communicate directly with other radios within a limited coverage area, without using the network infrastructure. DMO is often used in situations where access to the TETRA network infrastructure is limited or unavailable.
A TETRA network coverage area is configured to include a predefined geographical area. In order to support radios outside of the network coverage area, some radios may be configured to include DMO gateway functions. These radios are herein referred to as DMO gateways. A DMO gateway includes additional capabilities for connecting associated radios, operating in the direct mode outside of the network coverage area, to the network infrastructure. As such, the DMO gateway is the connection between trunked network devices, such as radios and base stations, and radios operating in the direct mode outside the network coverage area. For example, a mobile radio in a police vehicle may be configured to connect associated radios, such as portable radios used by police officers assigned to the police vehicle, to the network infrastructure, when the portable radios are outside of the network coverage area. Accordingly, if the mobile radio in the police vehicle is in a geographical location close the boundary of the network coverage area, and if the police officer moves to a location outside of the network coverage area, the police officer may still communicate with, for example a central dispatch center or other radios on the trunked network, by sending information directly from a portable radio to the mobile radio (DMO gateway). The DMO gateway may thereafter transmit the information to other network devices through the network infrastructure.
By default, a radio configured to function as a DMO gateway is generally set up to operate in trunked mode. In order for the radio to function as a DMO gateway, a DMO gateway mode must be manually activated by, for example flipping a switch on the radio. When the DMO gateway mode is not activated, radios associated with the DMO gateway will be unable to communicate directly with the DMO gateway.
In some situations, there may be multiple DMO gateways in a given location. There is a possibility of these DMO gateways attempting to use the same DMO channel, which may lead to interference. For example, during an emergency there may be multiple police vehicles, each with its mobile radio configured to function as a DMO gateway in a given location. If, the DMO functions for two or more mobile radios are activated when sufficiently close to each other, there is likely to be interference when these DMO gateways attempt to use the same DMO channel.
Accordingly, there is a need for a method and apparatus for dynamically enabling a DMO gateway and for minimizing potential interference between DMO gateways.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.